Tải bản đầy đủ - 0 (trang)
Table 309A. Distribution of Loss of Hearing Acuity

Table 309A. Distribution of Loss of Hearing Acuity

Tải bản đầy đủ - 0trang

316



T A B L E 310.-ARCHITECTURAL



FIG.3.-Attenuation



T A B L E 310A.-OPTIMUM



ACOUSTICS (concluded)



coefficient nz per foot as a function of humidity.



R E V E R B E R A T I O N T I M E (FIGS. 4 A N D 5 )



T h e following figures give the recommendations of Knudsen and Harris for optimum

reverberation time for different types of rooms as a function of room volume. The optimum

times for speech rooms, motion-picture theaters, and school auditoriums are given by a

single line ; the optimum time for music by a broad band. Th e optimum reverberation time

is not the same for all kinds of music. F o r example, slow organ and choral music require

more reverberation than does a brilliant allegro composition played on woodwinds, piano,

or harpsicord.

The optimum reverberation time vs. frequency characteristic for a room can be obtained

from these charts in the following manner : After having specified the volume and purpose

of the room, determine the optimum reverberation time at 512 cycles from the upper chart.

Then, to obtain optimum reverberation time a t any other frequencies multiply the 512-cycle

value by the appropriate ratio R which is given in the lower chart. Note that R is unity

for frequencies above 500 cycles, and is given by a band for frequencies below 500 cycles.

The ratio R for large rooms may have any value within the indicated band; preferred

ratios for small rooms are given by the lower part of the band.

(corztinued)



SMITHSONIAN PHYSICAL TABLES



T A B L E 310A.-OPTIMUM



FIG.4.-Optimum



REVERBERATION T I M E (FIGS. 4 A N D 5)

' < c o d I Ub&)



317



reverberation time as a function of volume of rooms for various types of

sound for a frequency of about 512 cycles per second.



1.6

1.6



1.4



4:



...



0 1.2

1.2

L



5



L



a! 1

1..c0I

0e

0I

00

100



FIG.S.--Ratio



200



so0 400



600 8001000



2000 3000



5000



10.000



FREQUENCY IN cYcLea PER SECOND

of the reverberation time for various frequencies as a function of the

reverberation for 512 cycles per second.



SMITHSONIAN PHYSICAL TABLES



318



TABLES 311-338.-VISCOSITY



OF F L U I D S A N D S O L I D S *



The coefficient of viscosity of a substance is the tangential force required to

move a unit area of a plane surface with unit speed relative to another parallel

plane surface from which it is separated by a layer of the substance a unit thick.

Viscosity measures the temporary rigidity it gives to the substance.

Fluidity is the reciprocal of viscosity expressed in poises. Kinematic viscosity is absolute viscosity divided by density. Specific viscosity is viscosity

relative to that of some standard substance, generally water at some definite

temperature. The dimensions of viscosity are J4L-lT-l. It is generally expressed in cgs units as dyne-second per cm2 or poises.

The viscosity of fluids is generally measured by one of several methods

depending on the magnitude of the viscosity value to be measured. For vapors

and gases as well as for liquids of low viscosity, measurements of viscosity are

made by the rate of flow of the fluid through a capillary tube whose length is

great in comparison with its diameter. The equation generally used is

T],the



viscosity, -



- 12852 (I+ A )



where y -is the density (g/cm3), d and I are respectively the diameter and

length in cm of the tube, Q the volume in cm3 discharged in t sec, h the

Couette correction to the measured length of the tube, h the average head in cm,

m the coefficient of kinetic energy correction, mvu2/g,

necessary for the loss of

energy due to turbulent, in distinction from viscous, flow, g being the acceleration of gravity (cm/sec2), 2, the mean velocity in cm/sec. (See Herschel, Nat.

Eur. Standards Techn. Pap. Nos. 100 and 112, 1917-1918, for discussion

of this correction and h . )

For liquids of medium and high values of viscosity measurements are made

by Margule's method of observing the torque on the inner of two concentric

cylinders while the outer is rotated with constant angular speed with the viscous liquid filling the space between, or by noting the rate of fall of a solid

sphere through the liquid.

For the method of concentric cylinders the equation is

K8(R12--R Z 2 ),

q, the viscosity, =

4&R,' R2, L

where K denotes the elastic constant of the torsion member supporting the

inner cylinder of radius R, cm and length L cm, .8is the angular displacement

of the inner cylinder from its position of equilibrium, R the angular speed of

the outer rotating cylinder of radius R , cm in the corresponding units employed to measure 8. The necessary corrections due to end effects of cylinders

of finite length are given in the reference.'O"

For the falling sphere method, the equation is that of Stokes law as modified

by R. G. Hunter: l o g



1 . R 2.2s )



T], the



('-71,



2 R2(d,-d2)

viscosity, = 9

(1+3.3:)



'



where y denotes the radius in cni of the crucible containing the liquid of density

d , (g/cni3), to a depth of Iz cni, R the radius in cm of the sphere of density d ,

(g/cm3), and Y the velocity (cni/sec) of the falling sphere.

* T h e data on viscosity were selected and arranged by George V. McCauley, Corning

Glkss Works.

Lillie, H . R., Journ. Amer. Cer. SOC.,

vol. 12, p. 505, 1929.

looHunter, R. G.. Journ. Amer. Cer. SOC.,

vol. 17, p. 123, 1934; Ann. d. Phys., ser. 4,

vol. 22, p. 287, 1907; vol. 23, p. 447, 1907.

SMITHSONIAN PHYSICAL TABLES



319

For very viscous materials, measurements of viscosity are made by noting

the rate of elongation of fibers under load or by observing the aperiodic inotioii

of an elastic system displaced from its position of equilibrium and damped by

the viscous material.

The formula for the rate of elongation of fibers as employed by H. R.

Lillie

is

Lxgxk

7, the viscosity, =

37rR2E '

where R is the radius in cni of the fiber of effective length, L (cm), g the

mass in grams of the attached load, k the acceleration of gravity (cm/sec2),

and E the rate of elongation in cm/sec.

For the aperiodic motion of the system consisting of the suspended inner

cylinder of Margule's apparatus described above, the formula is

K(t,-t,) log e R Z 2 - R l 2

7 , the viscosity, =

el R12RZZ

4XL log,, -



)'



(



0,



where t2 and t , denote the times in seconds of angular positions O2 and 8, of the

suspended system from its position of equilibrium. The other characters have

the same significance as in the formula above for the rotating cylinder method

of measuring viscosity. (For reference, see footnote 105.)

The viscosity of solids may be measured in relative terms by the damping

of the oscillations of suspended wires (see Table 323). Ladenburg (1906)

gives the viscosity of Venice turpentine at 15.3" as 1300 poises; Trouton and

Andrews (1904) of pitch at O o , 51 x lo'", at 15") 1.3 x 1O'O; of shoemaker's

~ of soda glass at 575", 11 x lo'*; Deeley (1908) of glacier

wax at 8", 4 . 7 lo6;

ice as 12 x 1013.

"'Lillie, H. R., Journ. Amer. Cer. SOC.,vol. 14, p. 502, 1931.



T A B L E 311.-VISCOSITY



OF W A T E R I N C E N T I P O I S E S



(Temperature variation)

Part 1.-Low

Vi?



CP



"C



Viscos1ty

cp



"C



20

21

22

23

24



1.0050

.9810

.9579

.9358

.9142



30

31

32

33

34



,8007

.7840

.7679

.7523

.7371



25

26

27

28

29



.8337

3737

,8545

.8360

.8180



35

36

37

38

39



,7225

.7085

.6947

.6814

.6685



"C



cos1ty

CP



"C



Viscosity

cp



"C



0

1

2

3

4



1.7921

1.7313

1.6728

1.6191

1.5674



10

11

12

13

14



1.3077

1.2713

1.2363

1.2028

1.1709



5 1.5188



15

16

17

18

19



1.1404

1.1111

1.0828

1.0559

1,0299



6

7

8

9



1.4728

1.4284

1.3860

1.3462



Viy

cosrty



temperature



(continued)



SMITHSONIAN PHYSICAL TABLES



Viy

cos1ty



cp



"C



Viscosity

cp



,5494

,5404

S315

,5229

S146



60

65

70

75

80



.4688

.4355

.4061

.3799

.3565



Vis.

cos1ty



cp



"C



40

41

42

43

44



.6560

.6439

,6321

.6207

.6097



50

51

52

53

54



45

46

47

48

49



S988

.5883



55 .SO64

56 .4985

57 .4907

58 .4832

59 .4759



.5782

.5683

S588



85 .3355

90 3165

95 .2994

100 2838

153 .181



320

O F W A T E R I N CEN TIPOIB ES (concluded)



T A B L E 311.-VISCOSITY



Pa rt 2.-High

viscosity

cp



"C



130

135

140

145

150

"'Based



...

...



...



.I99

.191



temperature"'



"C



viscosity

cp



"C



cp



"C



155

160

165

170

175



.184

.178

.173

.I66

.I60



180

185

190

195

200



.I55



205

210

215

220

225



Vi,s-



Vis-



COSItY



COSltY



.I51

.146

.I43

.139



cp



.136

.134

.131

.129

.128



on measurements by Shugayev, V., Journ. Exp. and Theoret. Phys. ( U . S . S . R . ) , vol. 4,



p. 760, 1934.



P a rt 3.-Viscosity



o f heavy water in centipoises



9.65% DzO; dn" = 1.10495



"c

4



5



6

7

112



Via-



Viy

cos1ty

CD



"c



COS'tY

CD



2.25

2.10

1.99

1.90



8

9

10

11



1.81

1.73

1.67

1.61



"C



Viy

cos1ty

cp



"c



12

13

14

15



1.56

1.51

1.46

1.41



16

17

18

19



VisCOSltY

CD



1.37

1.33

1.29

1.25



Data by Lemond, Henri. Cornpt. Rend., vol. 212, p. 81, 1941.



T A B L E 312.-VISCOSITY



O F AL COHOL -W AT E R



M I X T U R E S I N CENTlPOlSES



(Temperature variation)

Percentage by weight of ethyl alcohol



"C



0



5



10



is



20



--



-



0



10



20



30



35



40



45



50



60



70



80



90



100



1.792

1.519

1.308

1.140

1.005



3.311

2.577

2.179

1.792

1.538



5.319

4.065

3.165

2.618

2.183



6.94

5.29

4.05

3.26

2.71



7.25

5.62

4.39

3.52

2.88



7.14

5.59

4.39

3.53

2.91



6.94

5.50

4.35

3.51

2.88



6.58

5.26

4.18

3.44

2.87



5.75

4.63

3.77

3.14

2.67



4.762

3.906

3.268

2.770

2.370



3.690

3.125

2.710

2.309

2.008



2.732

2.309

2.101

1.802

1.610



1.773

1.623

1.466

1.332

1.200



2.35

2.00

1.71

1.473

1.284

1.124



2.35

2.02

1.72

1.482

1.289

1.132



2.39

2.02

1.73

1.495

1.307

1.148



2.40

2.02

1.72

1.499

1.294

1.155



2.23

1.93

1.66

1.447

1.271

1.127



2.037

1.767

1.529

1.344

1.189

1.062



1.748

1.531

1.355

1.203

1.081

968



1.424 1.096

1.279 1.003

1.147 .914

1.035 ,834

.939 .764

348 .702



.a5



.893

.727

.601



.907

.740

.609



,913

.740

.612



,902

.729

.604



.856

.695

-



.789

.650

-



25

30

35

40

45

50



394 1.323 1.815 2.18

301 1.160 1.553 1.87

.722 1.006 1.332 1.58

.656 .907 1.160 1.368

.599 312 1.015 1.189

.549 ,734 907 1.050



60

70

80



.469

.406

.356



.609

.514

.430



.736

.608

SO5



SMITHSONIAN PHYSICAL TABLES



,834

.683

.567



,725

.598



,704

.589



.592

504



- -



Tài liệu bạn tìm kiếm đã sẵn sàng tải về

Table 309A. Distribution of Loss of Hearing Acuity

Tải bản đầy đủ ngay(0 tr)

×